Re: [PATCH] tracing/user_events: Run BPF program if attached
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2023-05-09 20:42:53
Also in:
bpf, lkml
On Tue, 9 May 2023 16:30:50 -0400 Steven Rostedt [off-list ref] wrote:
quoted
From the user space side, which does:https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/user_events/example.c#n60 /* Check if anyone is listening */ if (enabled) {
Hmm, looking at this deeper, we should update it to prevent the
compiler from optimizing it, and keeping "enabled" in a register. Which
would not work. Should probably add:
if (*(const volatile int *)&enabled) {
-- Steve
/* Yep, trace out our data */
writev(data_fd, (const struct iovec *)io, 2);
/* Increase the count */
count++;
printf("Something was attached, wrote data\n");
}